Micro electro mechanical system, semiconductor device, and manufacturing method thereof

ABSTRACT

The present invention provides a MEMS and a sensor having the MEMS which can be formed without a process of etching a sacrifice layer. The MEMS and the sensor having the MEMS are formed by forming an interspace using a spacer layer. In the MEMS in which an interspace is formed using a spacer layer, a process for forming a sacrifice layer and an etching process of the sacrifice layer are not required. As a result, there is no restriction on the etching time, and thus the yield can be improved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a minutestructure body and a manufacturing method thereof.

2. Description of the Related Art

MEMS (micro electro mechanical system) technology which is applied forelectronic parts such as a filter, sensors or actuators has beendeveloped.

MEMS is formed using a silicon wafer, has a structure layer forming aninterspace, and includes an etching process of a sacrifice layer of thesilicon wafer so as to form the interspace. The etching process of asacrifice layer is a process for forming an opening in the lateraldirection to form an interspace, not a process for an opening in thevertical direction as conducted in a manufacturing process of asemiconductor integrated circuit.

As just described above, MEMS has a feature that a substrate isprocessed three-dimensionally and is essentially different from amanufacturing process of a semiconductor integrated circuit in which acircuit pattern is formed two-dimensionally. Thus, the etching processin manufacturing MEMS takes time and yield is poor, since a form to beprocessed by the etching is complicated.

For example, in order to shorten the time needed for etching a sacrificelayer, a tunnel structure is formed inside the sacrifice layer byproviding the sacrifice layer in two-layer form, and thus, an etchingsolution goes into the sacrifice layer fast through the tunnel structureat the time of etching of the sacrifice layer (for example, Reference 1:Japanese Published Patent Application No. 2000-58866).

SUMMARY OF THE INVENTION

However, in the case of the sacrifice layer in two-layer form, theetching process is inevitable and it is difficult to simplify andshorten the manufacturing process. In addition, it has thus beendifficult to improve the manufacturing yield.

The present invention has been made in view of the above problems. It isan object of the present invention to provide an easy manufacturingmethod of a micro electro mechanical system and a semiconductor deviceincluding the micro electro mechanical system.

In accordance with the present invention, in a micro electro mechanicalsystem having an interspace and a semiconductor device including themicro electro mechanical system and an electric circuit, an interspaceto secure a work area of the micro electro mechanical system is formedusing a spacer layer having adhesiveness which is formed selectivelybetween a substrate and a functional layer. Specifically, a MEMS (alsoreferred to as a micro electro mechanical system) in which an interspaceis formed using a spacer layer is formed in accordance with the presentinvention. A device including the micro electro mechanical system likethis and an electric circuit is referred to as a semiconductor device.Such an electric circuit is mainly formed from a semiconductor elementand the like, and the semiconductor device can have a structure enablingwireless communication.

Hereinafter, the specific structure examples of the present inventionare shown.

One mode of a micro electro mechanical system of the present inventionis that a first spacer layer, a layer including a piezoelectric element,a second spacer layer and a second film substrate are formed over afirst film substrate. Here, the layer including the piezoelectricelement includes the piezoelectric element formed by stacking a firstelectrode, a piezoelectric material and a second electrode. The numberof the piezoelectric elements included in the layer including thepiezoelectric element may be one or more. The first spacer layer and thesecond spacer layer are selectively formed using materials havingadhesiveness so as to form an opening portion to be overlapped with thepiezoelectric element provided in the layer including the piezoelectricelement.

In addition, the area of the opening portion is larger than the area ofthe piezoelectric material forming the piezoelectric element,specifically, the distance between an end of the piezoelectric materialand an end of the opening is preferably 10 μm or more and 100 μm orless. Further, the first spacer layer and the second spacer layer mayhave forms to be considered to be similar (or about the same form), andmay be stacked over a region to be considered to be similar (or aboutthe same region). Therefore, the plural interspaces can be disposed tobe overlapped.

Another mode of a micro electro mechanical system of the presentinvention is that a first spacer layer, a functional layer, a secondspacer layer and a second film substrate are formed over a first filmsubstrate. Here, the functional layer can be applied to not only apiezoelectric element but also particular functional elements which canbe formed by stacking thin films, for example, a passive element and anactive element such as a semiconductor element, a thermoelectricelement, a strain resistor element, an inductor and a capacitor. Thenumber of particular functional elements included in the layer may beone or more, and further, one kind or plural kinds of particularfunctional elements may be used. As in the above mode, the first spacerlayer and the second spacer layer are selectively formed using materialshaving adhesiveness so as to have an opening portion in a particularportion. Specifically, in the particular portion, the opening portion isprovided to be overlapped with the particular functional elementprovided in the layer including the particular functional element orwith an electrode electrically connected to the particular functionalelement.

Further, it is preferable that the first spacer layer and the secondspacer layer have a form to be considered to be similar (or the sameform), and be stacked over a region to be considered to be similar (orthe same region). Therefore, a plurality of interspaces can be disposedto be overlapped.

Next, one mode of a manufacturing method of a micro electro mechanicalsystem of the present invention is that a peeling layer, a layerincluding a piezoelectric element, and a first spacer layer are formedover a substrate, and a first film substrate is attached thereonto. Byutilizing the attachment of the layer including a piezoelectric elementto the first film substrate by the adhesiveness of the first spacerlayer, the layer including a piezoelectric element is peeled from thesubstrate and transferred to the first film substrate. After that, thesecond film substrate in which the second spacer layer is selectivelyformed is attached to the side of the layer including a piezoelectricelement with which the substrate has been in contact.

Another mode of a manufacturing method of a micro electro mechanicalsystem of the present invention is that a peeling layer, a functionallayer including a particular functional element, and a first spacerlayer are formed over a substrate, and a first film substrate isattached thereonto. By utilizing the attachment of the functional layerto the first film substrate by the adhesiveness of the first spacerlayer, the functional layer is peeled from the substrate and transferredto the first film substrate. After that, the second film substrate inwhich the second spacer layer is selectively formed is attached to theside of the functional layer substrate with which the substrate has beenin contact.

The two modes of the manufacturing methods of a micro electro mechanicalsystem are each made to satisfy conditions for constituting the microelectro mechanical system. For example, the area of the opening portionis 0.01 mm² or more and 25 mm² or less. The total area of the openingportion provided in the first spacer layer is 20% or less of the wholearea of the first spacer layer.

Then, one mode of a semiconductor device of the present invention isthat a layer including an electric circuit, an electrode electricallyconnected to the electric circuit, a first spacer layer, a layerincluding a piezoelectric element, a second spacer layer and a secondfilm substrate are formed over a substrate. Here, the layer includingthe piezoelectric element, the first spacer layer and the second spacerlayer have the same structure as those of the above-described microelectro mechanical system.

Another mode of a semiconductor device of the present invention is thata layer including an electric circuit, an electrode electricallyconnected to the electric circuit, a first spacer layer, a functionallayer including a particular functional element, a second spacer layerand a second film substrate are formed over a substrate. Here, thefunctional layer, the first spacer layer and the second spacer layerhave the same structure as those of the above-described micro electromechanical system.

In the two modes of the semiconductor device, the electric circuitincludes a semiconductor element, and the electrode to be connected tothe electric circuit is formed so as to connect the electric circuitwith the piezoelectric element. In addition, the substrate constitutingthe semiconductor device is a film substrate, and a third spacer layermay be provided between the substrate and the layer including theelectric circuit. Further, in the two modes, the second spacer layer canbe formed with an anisotropic conductive adhesive agent.

One mode of a manufacturing method of a semiconductor device of thepresent invention is that a peeling layer, a layer including apiezoelectric element, and a first spacer layer are formed over a firstsubstrate, and a first film substrate is attached thereonto. Byutilizing that the layer including a piezoelectric element is attachedto the first film substrate by the adhesiveness of the first spacerlayer, the layer including a piezoelectric element is peeled from thesubstrate and transferred to the first film substrate. Then, a layerincluding an electric circuit, and an electrode electrically connectedto the electric circuit are formed over a second substrate. Then, asecond spacer layer is selectively formed either over the electrodeformed over the layer including an electric circuit or the side of thelayer including a piezoelectric element with which the substrate hasbeen in contact, and the face on which an electrode for the layerincluding an electric circuit is formed is attached to the side on whichthe layer including a piezoelectric element has been in contact with thesubstrate.

In addition, another mode of a manufacturing method of a semiconductordevice of the present invention is that a peeling layer, a functionallayer including a particular functional element, and a first spacerlayer are formed over a first substrate, and a first film substrate isattached thereonto. By utilizing the attachment of the functional layerto the first film substrate by the adhesiveness of the first spacerlayer, the functional layer is peeled from the substrate and transferredto the first film substrate. Then, a layer including an electric circuitand an electrode electrically connected to the electric circuit areformed over a second substrate. Then, a second spacer layer isselectively formed either over the electrode formed over the layerincluding an electric circuit or the side of the functional layer withwhich the substrate has been in contact. Then, the face on which theelectrode for the layer including an electric circuit is formed isattached to the side on which the functional layer has been in contactwith the substrate.

Further, in the two modes of a manufacturing method of a semiconductordevice, a peeling layer may be provided between the second substrate andthe layer including an electric circuit, and the second substrate may bepeeled from the layer including an electric circuit, so that the layerincluding an electric circuit is transferred to the first filmsubstrate. Because the layer including an electric circuit is attachedto the first film substrate, the layer including an electric circuit canbe peeled off from the second substrate by giving a change to thepeeling layer. After that, a second film substrate can also be attachedto the peeled surface of the layer including an electric circuit througha third spacer layer having adhesiveness.

In accordance with the present invention in which an interspace isformed using spacer layers, processes of forming a sacrifice layer andetching the sacrifice layer are not required. As a result, there is norestriction on the etching time, and the yield can be improved. Further,an expensive etching apparatus is not required.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C show a micro electro mechanical system according to oneaspect of the present invention;

FIGS. 2A to 2C show a micro electro mechanical system according to oneaspect of the present invention;

FIGS. 3A to 3D show a micro electro mechanical system according to oneaspect of the present invention;

FIGS. 4A to 4D show a substrate for a piezoelectric element according toone aspect of the present invention;

FIG. 5 shows a TFT substrate according to one aspect of the presentinvention;

FIGS. 6A and 6B show a micro electro mechanical system according to oneaspect of the present invention;

FIGS. 7A and 7B show a micro electro mechanical system according to oneaspect of the present invention;

FIG. 8 is a block diagram showing a semiconductor device according toone aspect of the present invention;

FIGS. 9A and 9B show an appearance of a semiconductor device accordingto one aspect of the present invention;

FIG. 10 shows an example of a pressure sensor according to one aspect ofthe present invention

FIG. 11 shows an example of a pressure sensor according to one aspect ofthe present invention;

FIGS. 12A and 12B are each an enlarged view of a pressure sensoraccording to one aspect of the present invention;

FIGS. 13A to 13C show a filter according to one aspect of the presentinvention; and

FIGS. 14A to 14C show a pressure sensor according to one aspect of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Modes

Hereinafter, the embodiment modes of the present invention will bedescribed with reference to the accompanying drawings. It is easilyunderstood by those skilled in the art that modes and details hereindisclosed can be modified in various ways without departing from thespirit and the scope of the present invention. It should be noted thatthe present invention should not be interpreted as being limited to thedescription of the embodiment modes to be given below. Note that in alldrawings showing the embodiment modes, the same reference numerals areused for the same portions or the portions having the same functions,and description thereof is omitted.

Embodiment Mode 1

Embodiment Mode 1 will describe a manufacturing process of a microelectro mechanical system in which an interspace is formed by usingspacer layers.

A substrate 100 is prepared as shown in FIG. 1A. As the substrate 100, asubstrate having an insulating surface (also referred to as aninsulating substrate) such as a glass substrate, a quartz substrate, ora plastic substrate can be used. For example, when a plastic substrateis used, a highly flexible and lightweight micro electro mechanicalsystem can be provided. In addition, a thin micro electro mechanicalsystem can be provided by thinning a glass substrate by grinding andpolishing, and so on. Further, a conductive substrate such as metal or asemiconductor substrate such as silicon can be used as the substrate100. An insulating layer can be formed on a surface of such a substrateto be used.

A layer having an element which has a particular function (hereinafter,also referred to as a first functional layer) 101 is formed over theinsulating substrate 100.

Then, as shown in FIG. 1B, a spacer layer 102 is selectively provided soas to form an opening portion over the first functional layer 101.

The spacer layer 102 preferably has an adhesive function. The spacerlayer 102 attaches the functional layer 101 to a sealing substrate to beformed later, and an interspace is formed between the second functionallayer 103 and the functional layer 101. An organic material or aninorganic material can be used as the spacer layer 102. As the organicmaterial, compounds such as acrylic resin, polyimide resin, melamineresin, polyester resin, polycarbonate resin, phenol resin, epoxy resin,polyacetal, polyether, polyurethane, polyamide (nylon), furan resin, ordiallyl phthalate resin can be used. In addition, many of such organicmaterials have an adhesive function. High-viscosity materials such asacrylic resin or polyimide resin can be formed by an application method,a spin coating method or a droplet-discharging method. Thedroplet-discharging method is a method in which a prepared compositionis discharged from a nozzle in response to an electric signal to form aslight amount of a droplet and the droplet is attached on a desiredposition, and is also referred to as an inkjet method. As the inorganicmaterial, silicon oxide, silicon nitride, and the like are given. Thesilicon oxide or silicon nitride can be formed by a CVD method or thelike.

In order to selectively form the spacer layer like this, for example, amask is formed in a region in which the spacer layer is not formed overthe first functional layer 101. As the mask, a material can be used,which has no affinity with a material for forming the spacer layer, andrepels the material for the spacer layer when the spacer layer is formedfrom above the mask, and by which the spacer layer is not formed in aportion in which the mask is formed. It is possible that the spacerlayer is formed over the first functional layer 101, and the spacerlayer is selectively formed by removing the mask. The manufacturingmethod like this is preferable when the spacer layer 102 is formed of anorganic material. In addition, there is a method in which a spacer layeris formed entirely over the first functional layer 101, and a region inwhich the spacer layer is not formed is removed. In other words, aresist mask is formed by a photolithography method over the spacer layerformed over the first functional layer 101, and the spacer layer in aportion in which a resist mask is not formed, is removed by etching toselectively form the spacer layer 102. The manufacturing method likethis can be applied when the spacer layer 102 is formed of an inorganicmaterial. Additionally, by using a photosensitive cured resin materialcalled a thick-film resist, the spacer layer is directly exposed tolight and developed to be selectively formed.

As shown in FIG. 1C, a second functional layer 103 is provided over thespacer layer 102. The second functional layer 103 can be selected fromthe same substrates which can be used for the insulating substrate. Aninterspace 104 is produced by providing the second functional layer 103over the spacer layer 102. In other words, the interspace 104 surroundedby the first functional layer 101 on its bottom side, the spacer layer102 on its lateral side, and the second functional layer 103 on its topside.

A three-dimensional structure formed using the spacer layer 102 asstated above, is applied to various uses by making the first functionallayer 101 and the second functional layer 103 function as follows:

-   (1) Each of the first functional layer 101 and the second functional    layer 103 is made to function as an electrode, in particular, the    first functional layer 101 is made to function as an electrode    having sensitivity to an impulse caused by temperature, sound,    voltage, or the like. In this manner, it may be possible to use the    three-dimensional structure as a micro electro mechanical system,    which senses the impulse caused by temperature, sound, voltage, or    the like, such as a piezoelectric element, a thermoelectric element,    or a strain resistor element.-   (2) The first functional layer 101 and the second functional layer    103 are respectively made to function as an electric circuit and a    layer including an element which deforms due to the impulse caused    by temperature, sound, voltage, or the like (for example, a    piezoelectric element, a thermoelectric element, and a strain    resistor element are listed). In this case, the element which    deforms due to the impulse caused by temperature, sound, voltage, or    the like can deform easily because of the existence of the    interspace 104. In this manner, it may be possible to use the    three-dimensional structure as a semiconductor device including a    micro electro mechanical system and an electric circuit.

It is to be noted that the interspace 104 is preferably filled with aninert gas such as nitrogen or a rare gas. This is because deteriorationof the first functional layer 101 can be prevented.

Next, a case where the micro electro mechanical system manufactured asdescribed above is peeled off from the substrate 100 will be described.

As shown in FIG. 3A, a peeling layer 106 is formed over the insulatingsubstrate 100, and the first functional layer 101 and the spacer layerare formed. The peeling layer 106 is formed from a metal layer or asemiconductor layer. As the metal layer, a single layer or a stackedlayer an element/elements selected from tungsten (W), titanium (Ti),tantalum (Ta), molybdenum (Mo), neodymium (Nd), nickel (Ni), cobalt(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), or iridium (Ir), or an alloy material or a compoundmaterial thereof can be used. The metal layer can be formed by asputtering method using a metal as a target. The metal layer formed asthe peeling layer has a thickness of 10 nm to 200 nm, preferably 50 nmto 75 nm. When a semiconductor layer is used as the peeling layer, itmay include silicon. The structure may have any of an amorphoussemiconductor, a semi-amorphous semiconductor (SAS) with a mixed stateof an amorphous state and a crystal state, and a crystallinesemiconductor. Such a semiconductor layer can be formed by a sputteringmethod, a CVD method, or the like. The semiconductor layer formed as thepeeling layer may have a thickness of 30 nm to 1 m, and 30 nm or less isalso possible, as far as the thickness is within a thin film formationlimit of a film formation apparatus.

Here, the number of opening portions may be one or more, and the area ofone opening portion is 0.01 mm² or more and 25 mm² or less. The totalarea of the opening portions is preferably smaller than the total areaof the spacer layer by 20 to 30%, in other words, it is preferably 70 to80% of the total area of the spacer layer. This is made so that thepeeling process can be conducted easily when also utilizing theadhesiveness of the spacer layer. For example, the area of the openingportion is larger than 70 to 80% of the spacer layer, the functionallayer may be left on the surface of the substrate at the time ofpeeling. On the other hand, in order to secure the function of theinterspace, the opening portion needs have a certain degree of size.Therefore, the area of the opening portions is set at 70 to 80% of thetotal area of the spacer layer.

As shown in FIG. 3B, the second functional layer 103 is provided overthe spacer layer 102. The material and the like of the second functionallayer 103 are the same as those of the above-described embodiment mode,and the first functional layer 101 and the second functional layer 103can be attached to each other, because the spacer layer 102 has anadhesive function. When the second functional layer 103 is provided overthe spacer layer 102, the interspace 104 is generated, which issurrounded by the first functional layer 101 on its bottom side, thespacer layer 102 on its lateral side, and the second functional layer103 on its top side.

After that, as shown in FIG. 3C, the insulating substrate 100 is peeledoff. At this time, the peeling can be done by utilizing the adhesivenessof the spacer layer 102 which is higher than the adhesiveness of thepeeling layer 106. The adhesiveness of the peeling layer 106 can bereduced by giving a chemical or a physical change thereto. Then, theinsulating substrate 100 can be peeled off. For example, when tungstenis used for the peeling layer 106, a heat treatment is conducted togenerate a change in its crystal structure, thereby reducing theadhesiveness. As a result, the peeling occurs at an interface betweenthe peeling layer 106 and the insulating substrate 100, at an interfacebetween the peeling layer 106 and the first functional layer 101, or atthe inside of the peeling layer 106, thereby peeling the insulatingsubstrate 100 off from the first functional layer 101. In addition, whena semiconductor layer including silicon is used for the peeling layer106, an opening portion which reaches the peeling layer 106 is providedand an etching agent is introduced to remove the peeling layer 106. As aresult, the insulating substrate 100 is peeled off from the firstfunctional layer 101. Gas or liquid can be used for the etching agentand an etching agent which selectively reacts only with the peelinglayer is used. For example, as the etching gent which selectively reactsonly with the semiconductor layer including silicon, halogen fluoride isgiven. As halogen fluoride, chlorine trifluoride (ClF₃) or hydrogenfluoride (HF) can be used.

In this manner, the insulating substrate 100 can be removed. Further,the peeling layer 106 which is left on a rear side of the firstfunctional layer 101 may be removed. Then, as shown in FIG. 3D, a filmsubstrate 107 may be provided on the rear side of the first functionallayer 101. When a film substrate is used also as the sealing substrate103, a thin micro electro mechanical system having high flexibility canbe provided. In addition, by providing a protective layer 108 on therear side of the first functional layer 101, intrusion of impurityelements can be prevented. As the protective layer 108, silicon oxide orsilicon nitride can be used. Moreover, the functional layer 101 and thefilm substrate 107 can be attached to each other by using an organiccompound or the like.

As described above, one feature of the present invention is that theinterspace is formed by using the spacer layer.

Embodiment Mode 2

Embodiment Mode 2 will describe another structure of a micro electromechanical system in which an interspace is formed by a spacer layer.

FIG. 2A shows a micro electro mechanical system having anotherstructure, and is different from the micro electro mechanical systemshown in FIG. 1C in that a sealing substrate 105 provided with anopening portion is formed. The other structures are the same as in FIG.1C and thus, description thereof is omitted. The opening portion of thesealing substrate 105 has almost the same form as the opening portionprovided in the spacer layer so as to be overlapped. In other words, theinterspace 104 is surrounded by the first functional layer 101 on itsbottom side, the spacer layer 102 and the sealing substrate 105 on itslateral side, and its top layer side is open. Like this, the form of theinterspace is not necessarily closed.

Here, the explanations of the first functional layer 101 and the spacerlayer 102 in the Embodiment Mode 1 are applied to the first functionallayer 101 and the spacer layer 102 in this Embodiment Mode 2.

In addition, as in the above-described embodiment mode, the number ofthe opening portions may be one or more, and the area of one openingportion is 0.01 mm² or more and 25 mm² or less. The total area of theopening portions is preferably smaller than the area of the spacer layerby 20 to 30%. The spacer layer has a thickness of 10 μm or more,preferably 200 μm or less so as to secure the function of the openingportion. Moreover, this is done so that a peeling process to bedescribed below is easily conducted.

Further, the opening portion is formed in accordance with an arrangementof the functional element included in the first functional layer 101.For example, in a semiconductor device where the first functional layer101 and the second functional layer 103 respectively include asemiconductor element and a micro electro mechanical system, an openingportion is provided over an electrode connected to the semiconductorelement, and a contact-type inspection of the semiconductor elementincluded in the first functional layer 101 or an electric circuit formedfrom the semiconductor element can be conducted. In general, theinspection is conducted before providing the sealing substrate; however,according to the structure of the present invention, operation can beconfirmed by contacting a probe with a wire or the like of the firstfunctional layer 101 thorough the opening portion.

In the case of performing the contact-type inspection like this, thearea of the opening portion is preferably 0.1×0.1 mm² to 1.0×1.0 mm² ormore. The depth of the opening portion is equal to a sum of thicknessesof the spacer layer 102 and the second functional layer 103. Thus, whenthe depth of the opening portion is shallow, the thickness of the spacerlayer 102 is small. When the opening portion is too deep, it isdifficult to conduct the contact-type inspection; thus, it is preferableto control the thickness of the spacer layer.

In addition, as in the above-described embodiment mode, the manufacturedmicro electro mechanical system can be peeled off from the substrate100. As shown in FIG. 2B, in the micro electro mechanical system, thepeeling layer 106, the functional layer 101 and the spacer layer areformed over the insulting substrate 100, and then the insulatingsubstrate 100 is peeled off. The formation method and the peeling methodof the peeling layer 106 can be the same as those of the aboveembodiment mode.

After that, as shown in FIG. 2C, the film substrate 107 may be providedon a rear side of the first functional layer 101. A protective layer 108is provided between the first functional layer 101 and the filmsubstrate 107. The film substrate 107 and the protective layer 108 canbe provided in the same manner as in the above embodiment mode. Inaddition, the protective layer 108 can be attached to the firstfunctional layer 101 after being formed over the film substrate 107. Inthis case, the protective layer 108 serves as an adhesive layer foradhering the film substrate to the first functional layer 101.

By providing an opening portion in the second functional layer 105 inthis manner, a contact type inspection of the first functional layer 101can be conducted even after transferring the first functional layer 101to the film substrate 107. For example, when the first functional layer101 is peeled off as described above, and transferred to the filmsubstrate 107, characteristics of the element included in the functionallayer are changed in some cases. In such a case, measurement of anelement or an electric circuit can be conducted before the peelingand/or after transferring, as described in this embodiment mode. In thismanner, measurement is conducted in each process, and thus the processcan be controlled.

As described above, one feature of the present invention is that theinterspace is formed by the spacer layer and the opening portion is alsoformed in the sealing substrate.

Embodiment Mode 3

Embodiment Mode 3 will describe a manufacturing method of a microelectro mechanical system having an interspace as described above, and asemiconductor device having an electric circuit formed from asemiconductor element.

As shown in FIG. 4A, a peeling layer 305 is formed over an insulatingsubstrate 300. The insulating substrate 300 and the peeling layer 305can be manufactured in the same manner as in the above-describedembodiment mode. A layer including a piezoelectric element 315 isprovided over the peeling layer 305 as the functional layer in theabove-described embodiment mode. The piezoelectric element 315 has astructure in which a piezoelectric material 311 is formed over a firstelectrode 310, and a second electrode 312 is formed over thepiezoelectric material (for example, ceramic material) 311. A film madeof an element selected from aluminum (Al), titanium (Ti), molybdenum(Mo), tungsten (W) or silicon (Si), or an alloy film using some of theelements described above can be used for the first electrode 310 and thesecond electrode 312. As the piezoelectric material (ceramic material)311 which becomes a piezoelectric layer(for example, ceramic layer), forexample, quartz (SiO₂), barium titanate (BaTiO), lead titanate (PbTiO₃),lead zirconate titanate (Pb(Zr,Ti)O₃), lead lanthanum zirconate titanate((Pb,La)(Zr,Ti)O₃), lithium niobate (LiNbO₃), lead metaniobate(PbNb₂O₆), polyvinylidene fluoride (PVDF), zinc oxide (ZnO), nitridealuminum (AlN), or tantalum oxide (Ta₂O₅) can be used for example. Thepiezoelectric material is an insulator which has no crystal center. Whenthe piezoelectric material is applied with power to be strained and thecrystal is polarized, charges are generated in the surface. This iscalled a piezoelectric effect. On the other hand, when the piezoelectricmaterial is applied with voltage, a strain is generated. This is calledan inverse piezoelectric effect. Accordingly, the piezoelectric materialis oscillated, when it is applied with an alternating voltage.

Here, the case in which the layer including the piezoelectric element315 is provided is shown as an example; however, a layer including aparticular functional element which can be formed by stacking thin filmscan be formed. Here, as the particular functional element, variousfunctional elements can be used, such as a passive element and anegative element, for example, a thermoelectric element, a strainresistor element, an inductor and a capacitor, in addition to apiezoelectric element.

After that, as shown in FIG. 4B, a spacer layer 302 is selectivelyformed over or on the side of the piezoelectric element. As shown inFIG. 4B, a portion in which the piezoelectric element is formed becomesa non-formation region of the spacer layer 302, i.e., an openingportion. Here, the piezoelectric element is formed by stacking the firstelectrode 310, the piezoelectric material 311 and the second electrode312. By providing the sealing substrate 303 over the spacer layer 302,an interspace 304 is generated. In other words, the interspace 304 issurrounded by the piezoelectric element 315 on its bottom side, thespacer layer 302 on its lateral side, and the sealing substrate 303 onits top side. When the piezoelectric element 315 like this is deformedby surrounding pressure, the voltage between the first electrode 310 andthe second electrode 312 is changed. By reading the change of thevoltage, the pressure can be measured.

The micro electro mechanical system having the piezoelectric elementlike this can be applied to sensors (typically, pressure sensors),actuators, oscillation circuits and filters.

As shown in FIG. 4C, the substrate 300 is peeled off. The peeling methodof the insulating substrate 300 is the same as the peeling method of theinsulating substrate 100 described in the above embodiment mode.

As shown in FIG. 4D, the peeling layer 305 may be removed. Then, a filmsubstrate or a protective film may be formed on a rear side of thepiezoelectric element 315.

As described above, the piezoelectric element which is adjacent to theinterspace formed using the spacer layer can be formed.

Next, a method for forming an electric circuit which is connected to thepiezoelectric element will be described with reference to FIG. 5. Here,the electric circuit includes a control circuit or the like whichcontrols the piezoelectric element 315 or receives an output signal fromthe piezoelectric circuit 315. The control circuit or the like is formedwith thin film transistors or the like. Note that in this specification,a substrate provided with a thin film transistor (TFT) is referred to asa TFT substrate.

A thin film transistor includes a semiconductor film, a gate electrode,a gate insulating film, a source electrode and a drain electrode, andcan be formed by a known method. The semiconductor film may beamorphous, microcrystalline or crystalline. When a highly crystallinesemiconductor film is used, electric characteristics of the thin filmtransistor can be enhanced and can be preferably used for an electriccircuit. In this embodiment mode, thin film transistors 211, 212 and 213are provided over the insulating substrate 200. Note that the thin filmtransistors 211, 212 and 213 are preferably provided over the insulatingsubstrate 200 with a peeling layer 205 therebetween so as to peel theinsulating substrate 200 off later. An insulating layer 218 ispreferably formed to planarize the surfaces of the thin filmtransistors. The insulating layer 218 is formed over the thin filmtransistors 211, 212 and 213 and opening portions are provided in theinsulating layer 218 to form source electrodes and drain electrodes. Thesource electrodes and the drain electrodes serve also as source wiresand drain wires respectively. An insulating layer 219 is formed over thesource electrode and the drain electrode, and a connection terminal 220connected to the source electrode, the drain electrode or the gateelectrode is formed over the insulating layer 219. In this embodimentmode, a mode in which the source wire or the drain wire is connected tothe connection terminal 220 is shown; however, a gate wire may beconnected. For example, when the connection terminal 220 is connected tothe gate wire, given that the voltage of the connection terminal 220 isequal to or higher than a desired voltage, the thin film transistorconnected to the gate wire is turned ON. Here, the insulating layer 218and the insulating layer 219 are formed so as to insulate each thin filmtransistor, wires over and under the thin film transistors, and wireswhich are adjacent to each other. The insulating layers are formed so asto planarize the top surface of the functional layer provided with athin film transistor or a wire. The insulating layers 218 and 219 can beformed from an inorganic material or an organic material. When anorganic material is used for the insulating layers, the planaritythereof can be easily enhanced. The connection terminal 220 ispreferably provided as a pad having a large area so as to make easyconnection with the piezoelectric element possible. In this manner, acontrol circuit including a thin film transistor can be formed.

Naturally, the control circuit can be formed with MOSFET manufactured ona silicon wafer. However, a thin film transistor formed over theinsulating substrate can be used to reduce the manufacturing cost.

Then, a piezoelectric element is attached to the TFT substrate so as toconnect the control circuit with the piezoelectric element. For example,as shown in FIG. 6A, the connection terminal 220 is connected to thefirst electrode 310 and the second electrode 312 of the piezoelectricelement in a connection region 316. When the piezoelectric element 315is formed, the peeling layer 305 is removed, thereby exposing the firstelectrode 310 and the second electrode 312. As the connection method, ananisotropic conductive agent (or anisotropic conductive film: ACF) 330can be used. The ACF can have conduction only in one direction, andthus, connection between the connection terminal 220 and the firstelectrode 310 and between the connection terminal 220 and the secondelectrode 312 can be made. The distance d between the anisotropicconductive agent 330 and the piezoelectric material forming apiezoelectric element, i.e., the distance d from an end of thepiezoelectric material to an end of the opening portion is preferably 10μm or more and 100 μm or less. An area of the interspace formed by theanisotropic conductive agent 330 is preferably larger than the area of aportion in which the piezoelectric material is provided.

The anisotropic conductive agent 330 serves also as a spacer layer. Inaddition, the anisotropic conductive agent is preferably formed in aregion which is considered to be the same as the spacer layer 302 (oralmost the same region). Further, it preferably has the form which canbe considered to be the same as the spacer layer 302 (or almost the sameform). Thus, the interspace formed by the spacer layer 302 can bedisposed to be overlapped with the interspace formed by the anisotropicconductive agent 330.

An interspace 334 is generated by selectively forming the ACF 330. Theinterspace 334 is surrounded by the insulating layer 219 and theconnection terminal 220 on its bottom side, the ACF 330 on its lateralside, and the piezoelectric element 315 on its top side. Accuracy can beenhanced by providing the interspaces 304 and 334 over and under thepiezoelectric element 315. However, when the ACF 330 is providedentirely without forming the interspace 334, the micro electromechanical system can be used as a pressure sensor.

After that, the insulating substrate 200 is peeled off. The peeling ofthe insulating substrate 200 is the same as the peeling method of theinsulating substrate 100 of the above embodiment mode. The semiconductordevice shown in FIG. 6A is manufactured as stated above.

As shown in FIG. 6B, a film substrate 360 is provided below the thinfilm transistors 211, 212 and 213. At this time, the film substrate 360may be provided after removing the peeling layer 205. If a filmsubstrate is used also for the sealing substrate 303, a semiconductordevice having thinness and highly flexibility can be provided.

In addition, in FIG. 7A, a semiconductor device having a micro electromechanical system in which the piezoelectric element 315 is inverted andattached to the TFT substrate, and the connection terminal 220 iselectrically connected to the connection region 316, is shown. Thepiezoelectric element is attached to the TFT substrate in a state thatthe insulating substrate 300 for the piezoelectric element 315 ispeeled; however, it may be attached to the TFT substrate in a state thatthe insulating substrate 300 is not peeled. An interspace 334 isgenerated by inverting the piezoelectric element 315 and attaching it tothe TFT substrate. The interspace 334 is surrounded by the insulatinglayer 219 and a part of the connection terminal 220 on its bottom side,the ACF 330 on its lateral side, and the piezoelectric element 315 onits top side. The other structures are the same as those in FIGS. 6A and6B, and thus description is omitted. It is to be noted that it ispreferable to provide a protective film 318 in contact with thepiezoelectric element 315 in order to prevent piezoelectric element 315from being damaged. The protective film 318 is preferably formed from aresin material such as polyimide, or epoxy resin; however, an inorganicmaterial such as silicon oxide, or silicon nitride may be used to formthe protective film 315 as long as the protective film 315 has athickness thin enough not to prevent the operation of the piezoelectricelement 315.

In this manner, by inverting the piezoelectric element and attaching it,there is no need that a wire of the connection region 316 isdeliberately exposed. In other words, because the piezoelectric elementis inverted and attached, the piezoelectric element can be attached tothe TFT substrate without peeling the insulating substrate 300 and canbe electrically connected to the connection terminal 220. Therefore, thenumber of steps can be expected to be reduced, as a result of invertingthe piezoelectric element and attaching it to the TFT substrate.

FIG. 7B shows a case in which the substrate 303 is provided through thespacer layer 302 in the structure of FIG. 7A. An interspace 344 isgenerated by providing the substrate 303 through the spacer layer 302.The interspace 334 is surrounded by the piezoelectric element 315 on itsbottom side, the spacer layer 302 on its lateral side, and the substrate303 on its top side. It is to be noted that the substrate 303 ispreferably formed from a resin such as polyimide, or epoxy resin to haveflexibility. The other structures are the same as those of FIG. 7A, anddescription thereof is omitted. The interspace 334, and 344 is filledwith a rare gas or an inert gas such as nitrogen gas. The semiconductordevice having a structure like this can be operated as follows. Firstly,it is to be noted that pressure of outside of the semiconductor,pressure in the interspace 334, and pressure in the interspace 344 arerespectively referred to as P1, P2, and P3 (in the initial state, valuesof P3 and P2 are equal). When a pressure difference between P1 and P2changes due to variation of P1, the substrate will deform, and capacityV1 of the interspace 334 will change. The change of capacity V1 willcause change of P2. As a result, a pressure difference between P2 and P3will cause deformation of the piezoelectric element 315. The signalcaused by the deformation of the piezoelectric element 315 will bedetected by the electric circuit having TFT 212.

The micro electro mechanical system having a plurality of interspaceslike this is expected to be used for applications utilizing a volumedifference of the interspaces. For example, when a micro electromechanical system is applied to a pressure sensor, a first interspacehaving a large volume, i.e., a large surface area, is used as adetection surface, and a second interspace having a smaller volume thanthe first interspace is used for detecting a pressure change, therebyincreasing detection sensitivity. In addition, the number of theinterspaces is not limited to two, and more than two interspaces may beprovided.

Embodiment Mode 4

Embodiment Mode 4 will describe a mode in which a micro electromechanical system is applied to a filter. As shown in FIG. 13A, a filterhas a rectification function in which a particular frequency band from acomposite wave in which a plurality of frequencies are overlapped, isallowed to pass through the filter or is blocked. In other words, acomposite wave which passes the filter can be obtained as a rectifiedwave. The filter can be used for electronic devices which conductwireless communication, such as portable phones, PDAs (personal digitalassistants), or cards including wireless chips.

FIG. 13B shows a structural example of a micro electro mechanical systemwhich can be applied to a filter. As in the above-described embodimentmodes, the ACF 330 is selectively formed over the TFT substrate providedwith the TFTs 211, 212 and 213, and the piezoelectric element 315 isattached so that the connection terminal 220 and a connection region ofthe piezoelectric element 315 are electrically connected. Thus, theinterspace 334 is generated. The interspace 334 is surrounded by theinsulating layer 219 and a part of the connection terminal 220 on itsbottom side, the ACF 330 on its lateral side, and the piezoelectricelement 315 on its top side. The piezoelectric element forming thefilter may be circular, oval or polygon. Further, a plurality ofpiezoelectric elements can be connected in parallel or in serial to forma filter. In the case where it is used as a filter, the surface of thepiezoelectric element 315 may be exposed. A protective film made of aninsulator may be provided over the piezoelectric element 315 so as tosecure the strength.

FIG. 13C shows a different structure from FIG. 13B in that thepiezoelectric element 315 is inverted and attached to the TFT substrate,and a plurality of interspaces are provided over and under thepiezoelectric element. The other structures are the same as in the aboveembodiment modes, and thus, description is omitted. Naturally, aplurality of interspaces can be provided, without inverting thepiezoelectric element 315 as in FIG. 13B. The interspace 344 providedover the piezoelectric element 315 is generated by attaching thesubstrate 303 through the spacer layer 302. In other words, theinterspace 344 is surrounded by the piezoelectric element 315 on itsbottom side, the spacer layer 302 on its lateral side, and the sealingsubstrate 303 on its top side. The interspace 344 may be formed to havethe same volume as the interspace 334. By making the volumes of theinterspace 334 and the interspace 344 equal, their inner pressures canbe made equal easily. The forms of the interspaces 334 and 344 may berectangular, circular, polygon or oval.

By forming a filter using a micro electro mechanical system of thepresent invention in this manner, processes of forming a sacrifice layerof a micro crystal structure body and etching the sacrifice layer arenot needed. As a result, there is no restriction on the etching time,and the yield can be improved. Further, an expensive etching apparatusis not required.

Embodiment Mode 5

Embodiment Mode 5 will describe a mode in which a micro electromechanical system is applied to a sensor. As shown in FIG. 14A, apressure sensor utilizes a phenomenon that one electrode of apiezoelectric element is connected to a constant voltage (for example, aground voltage (GND)), and a voltage of the other electrode is changedby the inverse piezoelectric effect of the piezoelectric element whichis deformed by being applied with pressure. The pressure sensor inputthis voltage change into a control circuit, and has a function ofamplifying or processing the voltage change and outputting it. Apressure sensor like this can be mounted as a part of a feedbackmechanism in controlling pressure fluctuation or the like inside a filmformation apparatus for example, in the case of controlling pressurefluctuation.

FIG. 14B shows a structural example of a micro electro mechanical systemwhich can be applied to a pressure sensor. As in the above-describedembodiment mode, an ACF 330 is selectively formed in the TFT substrateprovided with the thin film transistors (TFTs) 211, 212 and 213 etc.,and the piezoelectric element 315 is inverted and attached so as toelectrically connect the connection terminal 220 and the connectionregion of the piezoelectric element 315. Thus, an interspace 334 isgenerated. The interspace 334 is surrounded by the insulating layer 219and a part of the connection terminal 220 on its bottom side, the ACF330 on its lateral side, and the piezoelectric element 315 on its topside.

When it is used as a pressure sensor, it is preferable that thepiezoelectric element 315 is not exposed. This is for maintainingsensitivity of pressure. Thus, in this embodiment mode, thepiezoelectric element 315 is inverted to form the interspace 334 and arear side of the piezoelectric element 315 is covered by a protectivefilm made of an insulator. The protective film is preferably formedusing a material which easily conducts pressure, more preferably, whichis easily deformed elastically but difficulty in deforming plastically.In the pressure sensor like this, the volume of the interspace 334 ischanged, i.e., external pressure can be measured by the change ofpressure.

FIG. 14C shows a pressure sensor having a different structure in that aplurality of interspaces are provided over and under the piezoelectricelement. The other structures are the same, and thus description isomitted. A detection face of pressure is preferably a face opposite tothe TFT substrate, and thus, in the case of using a micro electromechanical system as a pressure sensor, the piezoelectric element may beinverted and attached to the TFT substrate. The interspace 344 providedover the piezoelectric element 315 is generated by attaching the sealingsubstrate 303 through the spacer layer 302. In other words, theinterspace 344 is surrounded by the piezoelectric element 315 on itsbottom side, the spacer layer 302 on its lateral side, and the sealingsubstrate 303 on its top side. The interspace 344 may be formed to havethe same inner pressure as the interspace 334. By providing theplurality of interspaces and making inner pressure of each interspacedifferent, sensitivity of detection can be increased. For example, afirst interspace having a large volume, i.e., a large surface area isused as a detection surface, even if a second interspace has a smallervolume, the detection surface of the second interspace is large, therebyincreasing detection sensitivity.

By forming a pressure sensor using a micro electro mechanical system ofthe present invention, processes of forming a sacrifice layer of a microcrystal structure body and etching the sacrifice layer are not needed.As a result, there is no restriction on the etching time, and the yieldcan be improved. Further, an expensive etching apparatus is notrequired. Moreover, by applying the piezoelectric element of the presentinvention, electrical power saving and simplification of a structure canbe tried to be achieved.

Embodiment Mode 6

Embodiment Mode 6 will describe a semiconductor device which has a microelectro mechanical system and which is capable of conducting wirelesscommunication.

FIG. 8 shows a detailed structure of an electric circuit 604 of asemiconductor device 601. The electric circuit 604 has functions ofreceiving an electromagnetic wave emitted from outside (here,reader/writer 607) to generate electric power for driving thesemiconductor device 601, and carrying out wireless communication withoutside. Therefore, the electric circuit 604 has a power source circuit611, a clock generating circuit 612, a modulating circuit 613, ademodulating circuit 614, a decoding circuit 616, an encoding circuit617, an information judging circuit 618, and the like, which arenecessary for wireless communication. Moreover, in some cases, theelectric circuit has a different structure depending on frequency or acommunication method of an electromagnetic wave used for the wirelesscommunication.

Moreover, the electric circuit 604 has functions of controlling themicro electro mechanical system 603, processing information from thereader/writer 607, and so on. Therefore, the electric circuit 604 has amemory, a memory controlling circuit, an arithmetic circuit, and thelike. FIG. 8 shows a structure in which the electric circuit 604 has amemory 621, a memory controlling circuit 622, an arithmetic circuit 623,a microstructure controlling circuit 624, an A/D converting circuit 625,and a signal amplifying circuit 626.

The power source circuit 611 has a diode and a capacitor, and can holdconstant voltage by rectifying alternating voltage generated at theantenna 602 and supply the constant voltage to each circuit. The clockgenerating circuit 612 has a filter or a frequency dividing circuit, bywhich a clock with required frequency can be generated based onalternating voltage generated at the antenna 602 and the clock can besupplied to each circuit.

An element including one or more piezoelectric elements manufactured inaccordance with the above-described embodiment modes can be applied tothe filter. The filter manufactured according to a manufacturing methodof the present invention can be formed to be integrated over the samesubstrate as other circuits. As a result, a troublesome step ofpackaging or occurrence of detective connections can be reduced. Here, afrequency of a clock generated by the clock generating circuit 612 isbasically equal to or lower than a frequency of the electromagnetic waveused for communication between the reader/writer 607 and thesemiconductor device 601. In addition, the clock generating circuit 612includes a ring oscillator and can produce a clock having an arbitraryfrequency by voltage input from the power source circuit 611.

The demodulating circuit 613 has a filter and an amplifying circuit, sothat a signal included in alternating voltage generated at the antenna602 can be demodulated. The demodulating circuit 613 has a circuithaving a different structure depending on a modulation method used forthe wireless communication. The decoding circuit 615 decodes a signalwhich has been demodulated by the demodulating circuit 113. This decodedsignal is a signal which has been sent from the reader/writer 607 ornot. The information judging circuit 617 has a comparing circuit and thelike, and can judge whether the decoded signal is a correct signal thathas been sent from the reader/wrier 607. If the signal is judged to becorrect information, the information judging circuit 617 can send asignal showing that the signal is correct to each circuit (such as thememory controlling circuit 622, the arithmetic circuit 623, or themicrostructure controlling circuit 624), and the circuit having receivedthe signal can carry out, predetermined operation.

The encoding circuit 616 encodes data to be sent from the semiconductordevice 601 to the reader/writer 607. The modulating circuit 614modulates the encoded data and sends the modulated data to thereader/writer 607 through the antenna 602.

The data to be sent to the reader/writer is data specific to thesemiconductor device stored in a memory or data obtained by a functionof the semiconductor device. The data specific to the semiconductordevice is data such as identification information, which is memorized ina nonvolatile memory of the semiconductor device, for example. The dataobtained by a function of the semiconductor device is, for example, dataobtained by the micro electro mechanical system, data to which certaincalculation has been conducted based on the data obtained by the microelectro mechanical system, and the like.

The memory 621 can have a volatile memory and a nonvolatile memory, andstore data specific to the semiconductor device 601 (identificationinformation), information obtained from the micro electro mechanicalsystem 603, and the like. Although FIG. 8 shows only one memory 621, itis possible to have a plurality of types of memories in accordance withthe kind of information to be stored and a function of the semiconductordevice 601. The memory controlling circuit 622 controls the memory 621in the case of reading information stored in the memory 621 and writinginformation in the memory 621. Specifically, the memory controllingcircuit 622 can generate a writing signal, a reading signal, a memoryselecting signal, and the like, and specify an address, and so on.

The microstructure controlling circuit 624 can generate a signal forcontrolling the micro electro mechanical system 603. For example, in thecase of controlling the microstructure 13 in accordance with aninstruction from the reader/writer 607, a signal for controlling themicro electro mechanical system 603 is generated based on the signaldecoded by the decoding circuit 615. In the case where data such as aprogram for controlling operation of the micro electro mechanical system603 is stored in the memory 621, a signal for controlling the microelectro mechanical system 603 is generated based on the data read fromthe memory 621. Besides, it can have a feedback function for generatinga signal for controlling the micro electro mechanical system 603 basedon data in the memory 621, data from the reader/writer 607, and dataobtained from the micro electro mechanical system 603.

The arithmetic circuit 623 can process data obtained from the microelectro mechanical system 603, for example. Moreover, the arithmeticcircuit 623 can carry out information processing and the like in thecase where the microstructure controlling circuit 624 has a feedbackfunction. The A/D converting circuit 625 is a circuit for convertinganalog data and digital data and transmits a control signal to the microelectro mechanical system 603. Alternatively, the A/D converting circuit625 can convert data from the micro electro mechanical system 603 andtransmit the data to each circuit. The signal amplifying circuit 626 canamplify a weak signal obtained from the micro electro mechanical system603 and transmits the amplified signal to the AID converting circuit625.

By using the semiconductor device like this, wireless communication canbe conducted.

Embodiment Mode 7

Embodiment Mode 7 will describe an appearance of a semiconductor device.

FIG. 9A is a perspective view showing an appearance of a semiconductordevice. A semiconductor device 380 is packed by sealing substrates 303and 360 made of film materials.

FIG. 9B shows a cross section taken along A-B of FIG. 9A. Here, FIG. 9Ashows a simplified view of the cross section of the semiconductor deviceshown in FIGS. 6A and 6B. As in the above-described embodiment modes,the semiconductor device 380 is covered with the sealing substrates 303and 360.

As described in the above embodiment modes, the interspace included inthe semiconductor device is controlled to have a reference pressure. Inthe case of measuring a pressure around the atmospheric pressure, theinterspace is in the atmospheric pressure or a pressure around theatmospheric pressure. For example, when it has a pressure lower than theatmospheric pressure, the electrodes of the piezoelectric element bendthe interspace side (inward). Then, when the semiconductor device isarranged in the interspace having a predetermined pressure, theelectrode state of the piezoelectric element is changed in accordancewith the pressure of the interspace. The pressure of the interspace canbe measured from the electrode state of the piezoelectric element. Thus,when a pressure of high vacuum is measured, the interspace is in vacuum.

By giving adhesiveness to one film substrate of the semiconductordevice, e.g., a surface of the sealing substrate 303, it can be attachedto an object whose pressure is to be measured. The sealing substrate 303is made of a film and it is so thin that it can conduct the pressurechange of the object to the semiconductor device 380 accurately.

Naturally, the sealing substrates 303 and 306 are so thin that a thinsemiconductor device having high flexibility can be provided.

Embodiment Mode 8

Embodiment Mode 8 will describe an example in which a semiconductordevice having a piezoelectric element described in the above embodimentmode is applied as a pressure sensor. In this embodiment mode, asemiconductor device functioning as a sensor is applied to a pressuresensor of a system which monitors air pressure of tires.

As shown in FIG. 10, a semiconductor device 803 is disposed in a tire801 with a wheel 802. The semiconductor device 803 may be providedinside the tire 801; however, since the tire may be broken, it ispreferably attached to a valve part of the wheel. The semiconductordevice 803 includes a plurality of piezoelectric elements and a controlcircuit which controls the plurality of piezoelectric elements. In thisembodiment mode, the semiconductor device 803 includes fourpiezoelectric elements, i.e., first to fourth piezoelectric elements 811to 814, and a control circuit 816 which controls the piezoelectricelements. Note that the number of the piezoelectric elements is notlimited to four, and a plurality of piezoelectric elements may beprovided. The first to fourth piezoelectric elements 811 to 814 may havea different sensitivity from each other. For example, by usingpiezoelectric elements having different detection areas, a piezoelectricelement which can measure a low pressure band and a piezoelectricelement which can measure a high pressure band are provided so as toachieve a wide measurement band. In addition, any one of thepiezoelectric elements is used as a reference element.

By using the semiconductor device 803 like this, a pressure change canbe obtained as a volume change and thus, change of a tire pressure canbe checked. As a result, a tire can be prevented from being puncturedetc., because of a reduced pressure of the tire. A pressure sensor ofthis embodiment mode can directly measure an air pressure of a tire, andthus, measurement accuracy can be increased.

In addition, in order to obtain information from the semiconductordevice 803, a reader/writer device may be disposed in a car. Thesemiconductor device 803 obtains driving power from an electromagneticwave emitted from the reader/writer, and conduct transmission andreception of information with the reader/writer through theelectromagnetic wave. Thus, the semiconductor device 803 includes anelectric circuit for wireless communication as shown in theabove-described embodiment modes. For example, the semiconductor deviceincludes an antenna 818, a memory 819 and a CPU (central processingunit) 820. Naturally, an inner battery may be incorporated in thesemiconductor device 803.

By incorporating a pressure sensor of this embodiment mode, a tirepressure can be monitored relatively easily on a daily basis, withoutgoing to a car maintenance shop such as a service station.

A temperature sensor may be included in addition to the pressure sensor.By using both the pressure sensor and the temperature sensor, accuracyof tire pressure monitoring can be increased.

By using a semiconductor device of the present invention, a sensorhaving a new structure can be provided.

Embodiment Mode 9

Embodiment Mode 9 will describe a mode of a semiconductor device whichmeasures pulse with a micro electro mechanical system.

A micro electro mechanical system of the present invention is extremelythin, and can be covered with a film substrate. Thus, the micro electromechanical system is extremely flexible, and can be attached to a curvedsurface, for example, can be wrapped around a surface of a biologic bodyor a human body.

FIG. 11 shows an example in which the semiconductor device 903 isattached to a wrist 901. In this embodiment mode, pulse is measured withthe semiconductor device 903 including six piezoelectric elements, i.e.,first to sixth piezoelectric elements 811 to 816. Note that the numberof piezoelectric elements is not limited to six, and a large number ofpiezoelectric elements may be provided. When a plurality ofpiezoelectric elements are provided in this manner, information of apiezoelectric element among the plurality of piezoelectric elements,which counts a maximum number of pulses, is output. By providing theplurality of piezoelectric elements in this manner, count errors ofpulse can be reduced.

The semiconductor device has a measurement face having a predeterminedsize and a large number of piezoelectric elements having a smaller areamay be arranged in array in the measurement face. As shown in FIG. 12A,for example, the semiconductor device 903 in which 5×4 piezoelectricelements are arranged in array is attached to the wrist 901. At thistime, piezoelectric elements which are arranged so as to check pulse ofa blood vessel 902 are referred to as the first to sixth piezoelectricelements 811 to 816.

In addition, a piezoelectric element having a certain degree of area maybe provided. The number of piezoelectric elements to be provided becomessmaller in accordance with the area of the piezoelectric elements. Asshown in FIG. 12B, for example, the piezoelectric element may have awidth which is almost equal to a width of the blood vessel, and thefirst to sixth piezoelectric elements 811 to 816 may be arranged alongthe blood vessel.

Further, the semiconductor device 903 can conduct wireless communicationby having such an electric circuit as the above-described embodimentmodes. For example, the semiconductor device 903 includes an antenna818, a memory 819 and a CPU 820. The semiconductor device 903 may alsoinclude an input portion 821 and a display portion 823. A user can inputhis/her information to the input portion 821 and obtain information fromthe display portion 823. For example, based on measured pulse, advice orinformation on health can be displayed on the display portion 823.

Moreover, in the case of measuring pulse while exercising, calorieconsumption can be calculated from the change of pulse or the like andshown. Additionally, while exercising, when more pulses than a desiredlevel is shown, an alarm may be sounded.

By using a semiconductor device of the present invention, a sensorhaving a new structure can be provided.

This application is based on Japanese Patent application No. 2005-302343filed on Oct. 17, 2005 with the Japanese Patent Office, the entirecontents of which are hereby incorporated by reference.

1. A micro electro mechanical system comprising: a first functionallayer; a second functional layer; and a spacer layer provided to forminterspace between the first and second functional layers, wherein thespacer layer comprises at least one of acrylic resin, polyimide resin,melamine resin, polyester resin, polycarbonate resin, phenol resin,epoxy resin, polyacetal, polyether, polyurethane, polyamide, furanresin, and diallyl phthalate resin.
 2. A micro electro mechanical systemaccording to claim 1, wherein each of the first and second functionallayers is an electrode of a sensor.
 3. A micro electro mechanical systemaccording to claim 1, wherein the spacer layer has adhesiveness.
 4. Anelectronic device comprising the micro electro mechanical systemaccording to claim
 1. 5. A semiconductor device comprising: an electriccircuit; a sensor electrically connected to the electric circuit andprovided over the electric circuit; and a spacer layer provided to forminterspace between the electric circuit and the sensor, wherein thespacer layer comprises at least one of acrylic resin, polyimide resin,melamine resin, polyester resin, polycarbonate resin, phenol resin,epoxy resin, polyacetal, polyether, polyurethane, polyamide, furanresin, and diallyl phthalate resin.
 6. A semiconductor device accordingto claim 5, wherein the sensor is one of a piezoelectric element, athermoelectric element, and a strain resistor element.
 7. Asemiconductor device according to claim 5, wherein the spacer layer hasadhesiveness.
 8. A semiconductor device according to claim 5, whereinthe electric circuit detects a signal from the sensor.
 9. Asemiconductor device according to claim 5, wherein the interspace isfilled with a rare gas or a inert gas.
 10. An electronic devicecomprising the semiconductor device according to claim
 5. 11. Asemiconductor device comprising: an electric circuit; a sensorelectrically connected to the electric circuit and provided over theelectric circuit; a first spacer layer provided to form first interspacebetween the electric circuit and the sensor; a substrate provided overthe sensor; and a second spacer layer provided to form second interspacebetween the electric circuit and the sensor, wherein each of the firstand second spacer layers comprises at least one of acrylic resin,polyimide resin, melamine resin, polyester resin, polycarbonate resin,phenol resin, epoxy resin, polyacetal, polyether, polyurethane,polyamide, furan resin, and diallyl phthalate resin.
 12. A semiconductordevice according to claim 11, wherein the sensor is one of apiezoelectric element, a thermoelectric element, and a strain resistorelement.
 13. A semiconductor device according to claim 11, wherein eachof the first and second spacer layers has adhesiveness.
 14. Asemiconductor device according to claim 11, wherein the electric circuitdetects a signal from the sensor.
 15. A semiconductor device accordingto claim 11, wherein each of the first and second interspace is filledwith a rare gas or a inert gas.
 16. An electronic device comprising thesemiconductor device according to claim
 11. 17. A manufacturing methodof a semiconductor device, comprising steps of; forming a peeling layerover a first substrate; forming a sensor over the peeling layer; forminga first spacer layer having adhesiveness over the sensor; forming a filmover the first spacer layer so as to form a first interspace between thesensor and the film; separating a set of the sensor, the film, and thefirst spacer layer from the first substrate; and attaching the set ofthe sensor, the film, and the first spacer layer to a second substrateincluding an electric circuit and a second spacer layer formed over theelectric circuit, wherein a second interspace is formed between thesensor and the film.
 18. A manufacturing method of a semiconductordevice according to claim 17, wherein each of the first and secondspacer layers comprises at least one of acrylic resin, polyimide resin,melamine resin, polyester resin, polycarbonate resin, phenol resin,epoxy resin, polyacetal, polyether, polyurethane, polyamide, furanresin, and diallyl phthalate resin.
 19. A manufacturing method of asemiconductor device according to claim 17, wherein the sensor is one ofa piezoelectric element, a thermoelectric element, and a strain resistorelement.
 20. A manufacturing method of a semiconductor device accordingto claim 17, wherein each of the first and second interspace is filledwith a rare gas or a inert gas.
 21. A manufacturing method of asemiconductor device according to claim 17, wherein the peeling layercomprises at least one of tungsten, titanium, tantalum, molybdenum,neodymium, nickel, cobalt, zirconium, zinc, ruthenium, rhodium,palladium, osmium, and iridium.